The invention relates to devices for locking a vehicle seat. More specifically, the invention relates to a device for locking a vehicle seat comprising a locking pawl, which is arranged for coming into engagement with a fixed fitting part in a closed position of the locking pawl, and a locking element, which is arranged for locking the locking pawl in said closed position.
Within the meaning of the present invention, a locking device of the aforementioned type may be used for anchoring a vehicle seat to the floor or for locking a pivotable backrest of a vehicle seat.
The fixed fitting part, with which the locking pawl is in engagement in its closed position when the locking device is used for anchoring a vehicle seat to the floor is, for example, a bolt fixed to the bodywork, which is encompassed by a jaw of the locking pawl in the closed position thereof. When the locking device is used for locking a pivotable backrest of a vehicle seat, the fixed fitting part is, for example, a bolt fastened to the C-column, whilst the locking device is mounted on the pivotable backrest. The locking element serves in both cases to lock the pivotable locking pawl in its closed position.
A requirement for a device for locking a vehicle seat is that the locking pawl should not open automatically during operation of the vehicle in which the vehicle seat is installed. This applies, in particular, in the event of an impact to the vehicle, in which large forces are able to act on the locking pawl, and which are able to exert on the locking pawl a torque in the direction of its open position, the locking element having to counteract such an opening moment in order to hold the locking pawl securely in its closed position. This may be achieved, for example, by the locking element bearing against the locking pawl in the closed position thereof by self-clamping of the bearing surfaces on both the locking pawl and the locking element. The bearing with a self-clamping between the bearing surfaces of the locking pawl and the locking element, however, has the drawback that the locking device moves with difficulty when the locking pawl is intentionally opened.
In a locking device disclosed in the document DE 699 24 145 T2, the locking element comprises a bearing surface which is without eccentricity relative to the pivot axis of the locking element, and the locking pawl also comprises a bearing surface cooperating with the bearing surface of the locking element and which in the closed position of the locking pawl is also without eccentricity relative to the pivot axis of the locking element. By this arrangement of the bearing surfaces, the bearing surfaces bear against one another without self-clamping, which promotes the smooth-running of the device. For increasing the safety of the locking device in the event of an impact, it is proposed in the document that two further opposing surfaces are spaced apart from one another beyond the bearing surfaces of the locking element and the locking pawl. As result, it is intended to be achieved that a movement of the locking pawl, in the sense of an opening moment, is not able to be transmitted to the locking element. In addition to the two bearing surfaces of the locking element and the locking pawl without eccentricity relative to the pivot axis of the locking element, said two elements comprise two further opposing bearing surfaces which in the closed position of the locking pawl bear against one another and extend approximately at right angles to the two actual bearing surfaces and form therewith an angle of more than 180°. The latter two bearing surfaces, however, do not have a locking action.
A drawback with said known locking device is that it is not possible to clamp the locking pawl in its closed position in engagement with the fitting part, such that rattling noises during operation of the vehicle may be reliably avoided.
A further locking device is disclosed in DE 44 39 644 C2. In this known locking device, the locking element is provided with a clamping surface which has such a high degree of eccentricity relative to the pivot axis of the locking element that it clamps the locking pawl in its closed position and namely without self-clamping. The absence of self-clamping between the clamping surface of the locking element and the clamping surface of the locking pawl, however, in the event of impact to the vehicle, may cause the clamping surface of the locking element to slip off the clamping surface of the locking pawl. In order to prevent the locking pawl in such a case from reaching its open position, the locking element additionally has a catch surface which is configured so that it extends parallel to a displacement path between an axis of curvature of the clamping surface of the locking element and the pivot axis of the locking element.
DE 100 48 127 B4 discloses a device for locking a vehicle seat, comprising a locking pawl and a locking element, the locking element being configured as a clamping eccentric, which is configured with an eccentrically curved surface for clamping the pawl, a locking element being present in the form of a stop which is effective in the event of an impact and in this case prevents opening of the locking element. To this end, the locking element in the form of a clamping eccentric comprises an oblong hole, via which the clamping eccentric is mounted on the pivot axis of the clamping eccentric, the locking element only being effective in the event of an impact, by the clamping eccentric being displaced relative to its pivot axis, whereby a portion of the clamping eccentric moves against the locking element. In this device, therefore, play is compensated via an eccentric contour on the locking element, whilst the slot permits a displacement of the locking element in the event of an impact, so that the locking element moves against a stop in order to prevent an opening of the locking pawl.
In the two known locking devices cited above, it may be regarded as a drawback that the eccentric clamping surface for clamping the locking pawl in its closed position, in order to avoid rattling noises, always has to produce a sufficiently large counter force in order to keep the locking pawl closed which, for example, has to be implemented by a sufficiently high level of spring force which increases the force expenditure in the case of intentional opening.
DE 10 2009 019 510 A1 discloses a device for locking a vehicle seat in which the locking pawl is able to be clamped in the closed position by means of a locking element which is both pivotable and movable in a translatory manner towards the locking pawl, so that rattling noises are able to be avoided. However, the additional cost in terms of construction is a drawback in this locking device, as in this device an additional control element is required for bringing about the pivoting movement, on the one hand, and the translatory movement, on the other hand.